Add initial distributor CLI skeleton

internal/app/app_test.go

@@ -0,0 +1,16 @@
+package app
+
+import "testing"
+
+func TestVersionString(t *testing.T) {
+	oldVersion := Version
+	t.Cleanup(func() {
+		Version = oldVersion
+	})
+
+	Version = "1.2.3"
+
+	if got, want := VersionString(), "distributor 1.2.3"; got != want {
+		t.Fatalf("VersionString() = %q, want %q", got, want)
+	}
+}